An article of footwear includes an upper and a sole assembly secured to the upper. At least one recess is formed in the sole assembly, and a retractable protrusion is positioned in each recess. The protrusion is configured to be contained substantially within an exterior surface of the sole assembly in a retracted position and to extend substantially beyond the exterior surface in an extended position. The footwear includes at least one reservoir containing a fluid, with each reservoir having a first chamber and a second chamber. The first and second chambers are in fluid communication with one another, the first chamber is positioned inwardly of the second chamber, and the second chamber is positioned proximate a retractable protrusion.